Ceto.

Ceto (Κητώ) (Kētṓ) means 'sea monster'. She was a sea goddess in Greek myths and legends. Ceto's parents were Pontus (Πόντος) (Póntos) and Gaia (Γαῖα) (Gaîa).

Phorcys (Φόρκυς) (Phórkos) was her consort. They had children: the Gorgons (Γοργώνες) (Gorgones), the Graeae (Γραῖαι) (graîa), Echidna (Ἔχιδνα) (Ékhidna), and Ladon (Λάδωνος) (Ladonos). The Nemean lion (Νεμέος λέων) (Leo Nemeaeus) and the Sphinx (σφίγξ) (phíx) were Ceto's children, too.

Also, Ceto had several siblings.

Graeae.

Graeae (Γραῖαι) were three sisters with one eye and tooth in Greek mythology. They shared them.

Their parents were Phorcys and Ceto. Also, Graeae were the relatives of Gorgons.

These old women had names: Deino, Enyo, and Pemphredo.

Perseus met with Graeae. Zeus's son asked these creatures about the Gorgons. Also, he took their eye. After witches helped him.

There are many different paintings about these monsters.